Punctureproof tube and sealing material therefor



NOV- 3, 1953 K. v. HARDMAN Er AL 2,657,729

PUNCTUREPROOF TUBE AND SEALING MATERIAL THEREFOR Filed June 27, 1950 WM @M `automobile, truck and bicycle tires.

Patented Nov. 3, 1953 PUNCTUREPROOF TUBE AND SEALING MATERIAL THEREFOR Kenneth V. Hardman, Upper Montclair, and Arthur J. Lang, Cedar Grove, N. J., assignors to H. V. Hardman Company, Inc., a corporation of New Jersey Application June 27, 1950, Serial No. 170,594 4 Claims. (CI. 152-347) This invention relates to an article of manufacture and a composition and method for use in making the article.

The invention is particularly useful in the manufacture of puncture-proof inner tubes for For this reason the invention will be rst illustrated by description in connection with such use.

Puncture-proof pneumatic tires have been under study and in limited use for 25 years or more. During this period, there has been developed a tube of sandwich wall on the road side of the tube. This construction includes rubber, butyl rubber, or other rubber substitute as the walls of the sandwich and a gummy mass between them. In the case of puncture of the tube and subsequent withdrawal of the puncturing means, the gummy mass ows into the puncture and seals it against loss of air.

In this type of puncture-proof tube, the gum used is ordinarily a mixture of unvulcanized rubber with a softener therefor. Asphalt is a common softener, the attempt being made to control the consistency of the gum by means of the proportion of asphalt to the rubber, the kind of asphalt chosen, and kind and proportion of fillers.

The limited use of puncture-proof tires has been due in part to problems that remain unsolved in the manufacture and use of such tubes.

It is -well known, for instance, that, the temperature of the inner tube of a motor tire varies o ver a wide range, from the lowest temperatures of winter to 200 to 250 F. in summer driving,

It is well known, also that the unvulcanized rubber of the gum layer is susceptible to extreme changes lin consistency and viscosity with temperature. At the highest temperatures of fast driving in hot weather, an unvulcanized rubber gum that is passable in winter may be so fluid as to flow through a puncture and not seal it against the escape of air or, under the influence of the strong centrifugal force to which the gummy mass is subjected, may flow and create unbalance of the tire. At the lowest winter temperatures, on the other hand, the unvulcanized rubber becomes rigid and too firm to close the puncture dependably.

' An additional dimculty with puncture-proof tubes has been the change in the unvulcanized rubber of the gum layer on aging, This gum layer has the property of withdrawing sulfur from the vulcanized rubber of the inner and outer layers of the sandwich with which the gum is in contact. The sulfur so withdrawn operates,

2 particularly at temperatures to which the mass is raised during driving, to cause curing and objectionable changes from the originally established properties of the gum layer.

Our invention provides a composition, method and article overcoming these disadvantages and giving a puncture-proof tire that is satisfactory at all temperatures within the wire range to which the tire is subjected during use and that retains those properties. v

Briey stated, our invention comprises the herein described composition including heat depolymerized natural rubber and a gelling agent therefor. The invention comprises also the puncture-proof pneumatic tube utilizing the said composition for sealing punctures that may be formed in the tube and the method of making the improved tube.

The invention will be rst described in connection with the attached drawings to which reference is made.

Fig. 1 is a cross section through the punctureproof tube.

Fig. 2 is an enlargement of afragment of the tube showing a penetrating nail.

Fig. 3 is an enlargement of a fragment of the tube showing punctures lled inv by our gummy mass.

Fig. 4 is a perspective view of the inner tube with the gummy mass applied during a step in the manufactureof the tube.

Fig. 5 is a top plan view of the assembly before vulcanization.

Fig. 6 is a perspective view of the road side of a modification of the invention partly broken away for clearness of illustration.

There is shown the puncture-proof tube with tubular element I0, a layer of our gummy composition I2 applied over the part of the said element that is towards the road when the tube is in use, and a covering layer I4 of material of the same composition as the element I0 applied'over the outside of the gummy composition I2.

Puncture by a nail I6 and the subsequent owing of the gummy composition into the holes I8, left when the nail is removed, are shown in Figs, 2 and 3.

Figs. 4 and 5 represent stages in the manufacture of the puncture-proof tube. The element I0 is one that has been formed by extrusion in a usual manner. At the stage shown in Figs. 4 and 5, the element is in uncured condition and suitably in collapsed form. Over it, there is spread the gummy layer I2 of width approxit? mately equal to 140 of the circumference of the tube When inated. Spreader 20 is shown in the position of applying the mass.

Over the layer l2 of gummy material, there is applied a sheet 22 of rubbery composition of the sametype as thatwhich composee the tubi.;-A lar element l0. This sheet may beprovided on the flaps, extending beyond the gummy mass, with a conventional cement (not shown) or with a tacky surface and adhered toy the element I0 at positions beyond the edges ofthelayer .[2, as shown.

The assembly so made is then cut'arrd the 'ends joined to form the circular pneu-matic tube and the Whole cured in usual mannerasina Watchcase mold.

In the modification shown in Fig. 6, fstripslZl extend from the cover layer 26 (correspondngzto I4 in the embodiment of Fig. 1) The strips cut through the gummy mass during the assembly f and serve to compartmentizelithe gummy mass'in the finishedtube.

As *to materials, the tubularelement te arrd the covering sheet M Yare constructed of -vulcanized rubber materiaLthis term including any one of the rubber orrubber s-ubstitute'materials in use at this time forfinner'tubes for automobile tires. Thus, the parts" Iva and I4 may be natural rubber, butadiene vand `lstyrene copolymer, or isobutylene and isoprene copolymersrknown as butyl rubber, all in vulcanized condition.

The gum layer inourv tube contains heatfdepolymerized rubber such-'asthat made'as de-V scribed in United States Patent No.' 2,349,549 issued to Hardman and'I-Iardman Varid 'entitled Method of'Making- Depolymerized Rubber Articles, issued May23, 1944. Thedepolymerized rubber contains no volatile solvents. 'It is preferably of low `viscosity Vas, for instance, 19,000 to 100,000 Vcent-ipoises f when i measured at '1 50 F.

With the depolymerized rubber we usea' geliing agent. The agent used must be 'oneri/bieb, in the proportion used Will cause curing-*ofthe 'depolymer-ized rubber compositionito a `soit gummy mass having the generalcharacteristics'ofa part- 1y `vulcanized tacky rubbercompound. A gelling agent that meets these general' requirements Yand may be used in sulfur itself in low proportion. The combination of thefheat 'depolymeriz'ed rubber `and 'the'low Vproportion of 1.sulfur is relatively insensitive to su1furwithdravvn from 'sheets t8 and Mduringuse. 'The combination does 'not harden to an objectionable extent dur-ing use, even in 'contact with the additional sulfur. 4

Other gelling'agentsthat may beJ used are ferric chloride,` Stanuous and starmi@ fzillride,` and benzoyl, and like VorganicperoXildes These. other selling agents are retarders 0f Sulfur VCuring olf deplymerizedrubber. AS a result-these .other agents .act also as vretarders,l They Ygivre not only vthe desired Vtype of V product initially .but also practically eliminate any vulcani-zation .by sulfur that migrates, during use of the puncture-- proof tube, from the cuter land vinner layers of theinner tube to the tacky composition'fbetween those layers.

If the sulfur is used, there may alsofand pref- `erably is used a conventional vulcanization accelerator, Asuch as zinc dibutyl dithiarbamate, mercaptobenzothiazole, and ltet-ran'iethylthiuranl disulfide.

AConventional anti-oXidants-'are also used in the sulfur-:composition as, for instance-phenyl betanaphthylamine (AgeRite-powdew .-diphenylamine lincorporation into the depolyrnerized rubber.

{The inventionfwill be further illustrated by l"desciiptionjiri'conrfection with the following specificexamples. VProportions here and elsewhere herein'are expressed as parts by weight.

EXANIPLE' l Parts Heat depolymerized rubber 100 Sulfur 1 Zinc oxide 5 Clay 2,() Anti-oxidant (Ant.ox) `1 Zinc 'butyl thocarbamate `1 ..5

The' compeundine'- is. performed 4in a, finixer of the vvkrledilla type. TQ Y effect. @wdr-dispersion of. ingredients. thefmixirlg is-carried outfatra high viscosity by withholding,- Y-i.r.1,itialiypar-t of vthe depolymeri,zeclfrubber-butaddiriefally of: the pref sifted dry ingredients. The mullingfproceedsvat this high viscositynntilfall the particles are; disnersed. Then the remaining; denelymerired'ruhf ber is added. At theelev-ated temperatures of melt 0r become fluides-does a thermoplastic liquid. yIieiiher does. the feomnesitien fbecome brittle or rigid at subfjzero-temperatures as does an unvulcanized rubber gel.

'EXAMPLEZ Parts Depolymer-ized rubber-low'viscosity '100 Sulfur f0.5 Zinc'ox-i'de A5 A .Parts Depolymerizedrubberof low .viscosity -100 'Parts Depolymerized rubber of low' viscosity '100 Clay 20 Zincroxide 5 Oleic acid -3 Dipentamethylene' thiuram rtetrasulde Al Parts Depolymerized rubber-ofl=ow-viscosity 100 Ferri-e ychloride (Feels) EXAMPLE 6 Parts Depolymerized rubber of low viscosity 100 Stannous chloride (SnClz) 5 Water 5 Procedures for Examples 5 and 6 These gelling agents cause the depolymerized rubber to 4gum at a slower rate than in the cases of Examples 2, 3, and 4. It is possible to apply the admixtures as outlined in Examples 3 and 4 and to vulcanize integrally with the tube structure provided a slow cure is permissible, as, for instance, in the vicinity of 2 hours at a temperature of approximately 275 F. However, if this is not desirable the compounds under Examples 5 and 6 may first be heated with agitation for a period of between 1 and 2 hours at a temperature of about 275 F. This time-temperature cycle advances the gum to an intermediate stage which still allows a free owing 'consistency when the intermediate compound is pumped or spread upon the road surface of the inner tube. The vulcanization of the tube then provides sufcient time and temperature to complete the gumming or partial solidication of these Examples 5 and 6 to a state comparable to a partially vulcanized depolymerized rubber which displays the surprising but inherent ability to retain its basic gum consistency over wide ranges of temperature.

EXAMPLE 7 Parts Depolymerized rubber of low viscosity 100 Benzoyl peroxide 5 EXAMPLE 8 Parts Depolymerized rubber of low viscosity 100 Quinone 5 Mercurio oxide 3 EXAMPLE 9 Parts Depolymerized rubber of low viscosity 100 Metadinitrobenzene 10 Lead oxide 10 The compounds of the last two examples are also slower in curing rate than present day inner tube curing cycles and, therefore, may be partly heat cured to an intermediate state and spread by pumping or coating upon the inner tube followed by integral curing with the tube itself.

It will be understood that it is intended to 'cover all changes and modications of the examples of the invention herein chosen for the purpose of illustration which do no constitute departures from the spirit and scope of the invention.

What we claim is:

l. A tube for a puncture-proof pneumatic tire comprising a tubular `element of vulcanized rubber material, a gummy mass disposed as a layer over the side of the said element that is towards the road during use in a tire, and a sheet of vulcanized material disposed' over the gummy mass and enclosing it between the said sheet and element, the gummy mass comprising heat depolymerized rubber and 'a gelling agent and the gelling agent being used in proportion toprodu'ce a gummy mass with the depolymerized rubber K but less than the amount causing the gummy mass to become rigid during use on long contact with the vulcanized material.

2. A tube as described in claim 1, the depolymerized rubber being of viscosity 19,000 to 100,000 centipoises when measured at 150 F. and the `gelling agent being sulfur.

3. A tube as described in claim 1, the gelling agent being sulfur in the proportion of 0.1 to 1 part for parts of the depolymerized rubber.

4. A tube as described in lclaim 1, the gelling agent being dipentamethylene thiuram tetrasulde.

KENNETH V. HARDMAN. ARTHUR J. LANG.

References Cited in the le of this patent UNITED STATES PATENTS Number Name Date 1,137,461 Clare Apr. 27, 1915 1,237,698 Reuter Aug. 21, 1917 1,249,181 Ostromislensky Dec. 4, 1917 1,751,817 Jones et al Mar. 25, 1930 2,255,779 Kent Sept. 16, 1941 2,349,549 Hardman et al. May 23, 1944 OTHER REFERENCES Rubber Age (New York), Vol. 66 of January 1950, pp. 419-422 inc. 

1. A TUBE FOR A PUNCTURE-PROOF PNEUMATIC TIRE COMPRISING A TUBULAR ELEMENT OF VULCANIZED RUBBER MATERIAL, A GUMMY MASS DISPOSED AS A LAYER OVER THE SIDE OF THE SIAD ELEMENT THAT IS TOWARDS THE ROAD DURING USE IN A TIRE, AND A SHEET OF VULCANIZED MATERIAL DISPOSED OVER THE GUMMY MASS AND ENCLOSING IT BETWEEN THE SAID SHEET AND ELEMENT, THE GUMMY MASS COMPRISING HEAT DEPOLYMERIZED RUBBER AND A GELLING AGENT AND THE GELLING AGENT BEING USED IN PROPORTION TO PRODUCE A GUMMY MASS WITH THE DEPOLYMERIZED RUBBER BUT LESS THAN THE AMOUNT CAUSING THE GUMMY MASS TO BECOME RIGID DURING USE ON LONG CONTACT WITH THE VULCANIZED MATERIAL. 